Thin film head components such as sensors are created by wafer processing. Typically, a layer of photoresist is added to define the width of the component positioned underneath, and exposed material is removed by various processes. As components become smaller, the lithographic patterns must also become smaller yet must maintain a high resolution to properly form the components.
To achieve the high resolutions required for new processes, 193 nm lithography is typically used. However, 193 nm photoresist is very soft, typically softer than the underlayer. If reactive ion etching (RIE) is used, the topography of the photoresist pattern tends to be destroyed because the photoresist etches away faster than the underlayer. If edges of the photoresist are reduced, i.e., the resolution is degraded, the edges of the component will be removed, resulting in a deformed component. Further, if too little photoresist remains, upon ion milling, the photoresist will completely erode away and the surface of the component sought to be protected will be damaged.
Prior art attempts to overcome the problem of photoresist erosion used thicker layers of photoresist. However, the photoresist tended to fall over during subsequent processing. It was found that only an aspect ratio of about 3 to 1 photoresist height/width or less was stable enough for further processing.
The requirement that the photoresist be kept thin created another problem. Thin layers of photoresist, made thinner by subsequent processing, are hard to remove from the wafer. For example, if the processing parameters require printing of a 50 nm wide photoresist pattern, the thickness of the photoresist is only 150 nm. After processing, the photoresist is very thin, and causes the problems mentioned above.
What is needed is a way to achieve high resolution with a thin photoresist pattern. What is also needed is a way to stop the RIE from damaging the component sought to be protected. What is further needed is a way to ease the liftoff process.